add failing test case for Github #71, internal property name mangling…

… is affecting how Jackson sees the property names, and is ugly when serializing as JSON

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/failing/Github71.kt

@@ -0,0 +1,20 @@
+package com.fasterxml.jackson.module.kotlin.test.failing
+
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
+import org.junit.Test
+import kotlin.test.assertEquals
+
+class TestGithub71 {
+    open class Identifiable {
+        internal var identity: Long? = null
+    }
+
+    @Test
+    fun testInternalPropertySerliazation() {
+        val json = jacksonObjectMapper().writeValueAsString(Identifiable())
+        assertEquals("{\"identity\":null}", json) // fails: {"identity$jackson_module_kotlin":null}
+        val newInstance = jacksonObjectMapper().readValue<Identifiable>(json)
+        assertEquals(Identifiable(), newInstance)
+    }
+}